Lightguides having light extraction structures providing regional control of light output

Abstract

Lightguides, devices incorporating lightguides, and processes for making lightguides are described. A lightguide includes light extractors arranged in a pattern on a surface of the lightguide. The pattern of light extractors is arranged to enhance uniformity of light output across a surface of the lightguide and to provide enhanced defect hiding. The efficiency of the light extractors is controlled by a shape factor. The areal density of the light extractors across the surface of the lightguide may be substantially constant or may decrease along the direction of propagation of light from the light source.

What is claimed is: 
     
       1. A lightguide, comprising light extractors arranged in a pattern on a surface of the lightguide, the pattern configured to enhance uniformity of light output across a surface of the lightguide and wherein an areal density of the light extractors varies inversely with extraction efficiency of the light extractors. 
     
     
       2. The lightguide of  claim 1 , wherein the fill factor of the light extractors is above a minimum fill factor that prevents a viewer from resolving individual light extractors. 
     
     
       3. The lightguide of  claim 1 , wherein the light extractors are recessed structures. 
     
     
       4. The lightguide of  claim 1 , wherein the lightguide is monolithic. 
     
     
       5. The lightguide of  claim 1 , wherein the extraction efficiency of the light extractors varies as a function of height or shape or both of the light extractors. 
     
     
       6. The lightguide of  claim 1 , wherein the light extractors are arranged to enhance the uniformity of light output over a continuous surface of the lightguide. 
     
     
       7. The lightguide of  claim 1 , wherein the light extractors are arranged to enhance the uniformity of light output in discrete regions of the lightguide. 
     
     
       8. The lightguide of  claim 7 , wherein the discrete regions are configured to illuminate keys of a keypad. 
     
     
       9. The lightguide of  claim 1 , wherein the light extractors are truncated aspheres. 
     
     
       10. The lightguide of  claim 1 , wherein the light extractors are one or more of hemispheres, truncated hemispheres, cones, and truncated cones. 
     
     
       11. A backlight, comprising:
 a light source configured to generate light; and 
 a lightguide, comprising light extractors arranged in a pattern on a surface of the lightguide, the pattern configured to enhance uniformity of light output across a surface of the lightguide, wherein an areal density of the light extractors decreases as illumination from the light source decreases. 
 
     
     
       12. The backlight of  claim 11 , wherein the fill factor of the light extractors is above a minimum fill factor that prevents a viewer from resolving individual light extractors. 
     
     
       13. The backlight of  claim 11 , wherein the light extractors are recessed structures. 
     
     
       14. The backlight of  claim 11 , wherein the lightguide is monolithic. 
     
     
       15. The backlight of  claim 11 , wherein the extraction efficiency of the light extractors varies as a function of height or shape or both of the light extractors. 
     
     
       16. The backlight of  claim 11 , wherein the light extractors are truncated aspheres. 
     
     
       17. The backlight of  claim 11 , wherein the light extractors are one or more of cones and truncated cones. 
     
     
       18. The backlight of  claim 11 , wherein the areal density of the light extractors is substantially constant or decreases in a direction of propagation of light from the light source. 
     
     
       19. The backlight of  claim 11 , further comprising:
 a first area of the lightguide having relatively higher illumination from the light source; 
 a second area of the lightguide having relatively lower illumination from the light source, the light extractors in the first area having substantially equal or greater areal density than the light extractors in the second area.